Let's Go leg is atrocious in comparison to NSMBUD and SMP leg
Idk have you seen those games sales?
Mario Party was already over 5 million at the end of 2018 and has been charting pretty high on NPD, Media Create & EMEAA charts in 2019.
Same with NSMB, its charting extremely high everywhere and has to have sold a few million already and has only been out for just over a month.
I'm not talking about software sales though, I'm talking about shifting hardware. A game can sell millions to a platform's existing audience but not bring in a significant amount of new customers.